Chest tubes are required any time air and/or liquid accumulates in the chest cavity, disrupting normal pulmonary or cardiac function. Suction is applied continuously to remove excess air and/or fluid from the chest until the internal wounds have healed, at which point the chest tubes can be removed. One of the most common uses of chest tubes is to drain the area around the heart after cardiac surgery.
Despite their benefits, current chest tube systems suffer from two major flaws. First, as liquid drains from the chest toward the suction container, it can pool in the drainage tubing and prevent the applied negative pressure from being transmitted to the chest. When this occurs, the pressure in the chest can be reduced to zero or even become positive. Second, clogs can form that obstruct the chest tube, which prevent the negative pressure from being transmitted to the chest and inhibit drainage. In fact, 36% of cardiac surgery patients experience chest tube clogging. When proper drainage is inhibited due to these factors, patients are at increased risk for accumulation of fluid around the heart, known as pericardial tamponade, which results in shock and can be fatal. Additionally, the lungs may be compressed, which can lead to respiratory compromise and can be fatal as well.
Pooling of liquid in the drainage line can theoretically be remedied by keeping the tubing straight from the patient to the collection container. However, this is nearly impossible in practice, as some slack is required to prevent accidental dislodging of the tube from the body. To combat clogging, clinicians use two methods known as milking and stripping. Milking refers to line manipulations such as lifting, squeezing, or kneading. Stripping refers to a pulling along the length of the tube with the thumb and forefinger to increase the amount of suction at the end of the tube. However, these methods have not been shown to be effective at improving chest tube suction or drainage. In fact, stripping has actually been discouraged because it is possible to create extremely high negative pressures (up to −370 cmH2O) that may damage the tissue.
In addition to these functional flaws, current systems also rely on measures of collected fluid volume and rate of chest air leak, which are subjective and lead to imprecision and inaccuracies in the measurements. As a result, clinicians make cautious clinical decisions based on these measurements, keeping patients in the hospital longer than necessary.